We had a smaller wilderness with bunk beds and was not pleased with it. If we had bought a bigger one like you are looking at we would probably still have it as the we had was too small. Otherwise we really liked the Wilderness.
You will get lots of advise here so I will give you just a few pointers. Go to every window and push on the walls around them if the wood gives there has been leakage and the walls are rotted. Also do the same around the door and the vents and AC units. Get on the roof and check for the condition up there. If you see the AC units sagging the roof, that is a sign that there could be leakage around them and water will accumulate there when it rains. If you are unsure about the roof, take it to an independent RV repair shop (avoid dealers as they will want to sell you a trailer and may not give you a true evaluation).
Outside the trailer examine the window, door, and around the water heater and fridge for signs of leakage. If there are gaps between the sealant and these places, this is another sign that there may be leakage.
The biggest thing it to look at the trailer like it is one its last leg and you are trying to find anything good about it. DO NOT glaze over problems as if they are not really that bad. Assume the worst possible scenario for each thing. We never had any problems with our wilderness except it was too small for the 5 of us. It pulled great and handled very well in crosswinds.
If we had a vehicle big enough to pull a TT, Wilderness would have been on my list. But we didn't and found the MH we bought, a rough gem for a great price. I have a bucket list of things we want to do to her but that is just to make her ours, and not just like every other one that is still in use.
Good luck and happy traveling.
